Selection of welding joint coefficient
Thread Content
This post was last edited by *AOL_1 on 2017-11-8 at 14:56. While reading GB150-2011 recently, I have doubts regarding the welding joint coefficient as follows: 1. The welding joint coefficient should be determined based on butt joints******: Do both Class A and Class B welding joints need to be taken into consideration? 2. Is the welding joint coefficient for the entire container, or can it be considered separately for components such as the cylinder and head? Specific feedback on the above two questions: Is the welding joint coefficient for small end caps manufactured as a single piece 1? ； Shell of seamless steel pipe welded by segmented group welding: Is the weld joint factor 1 when 20% of the circumferential seams are inspected? Is it appropriate for a reputable textbook to assign a welding joint coefficient of 1?
1. The welding joint factor should be determined based on the butt joints******: Are both Class A and Class B welding joints required to be taken into consideration? Answer: The welding joint factor is determined based on the weld pattern of the butt joint and the length proportion of non-destructive testing. Butt joints represent Class A/B welds. 2. Is the welding joint coefficient for the entire container, or can it be considered separately for components such as the cylinder and head? Answer: Regarding the welding joint coefficient in the technical data sheet, whether the head and the cylinder should be specified separately varies from one company to another. Some are written in two columns, while others have only one. However, for the welding joint coefficient of the head, it remains 1.0 regardless of whether the cylinder’s coefficient is 0.85 or 1.0 ； It’s just that the inspection proportions are different; the acceptable quality levels remain the same for the same type of cylinder. For example, if the overall welding joint coefficient for the equipment is 0.85 with 20% RT inspection, then the acceptable quality level for that equipment is 20% RT-Grade III. For the end caps, the acceptable quality level is 100% RT-Grade III. Is the welding joint coefficient for small end caps manufactured from whole plates also 1? ； Answer: Yes, it is the shell of a seamless steel pipe welded in segments; 20% of the circumferential welds are inspected to determine whether the welding joint factor is 1. Answer: 20%, the welding joint factor is 0.85
The welding joint coefficient for small end caps manufactured as a single plate is 1； Shell of seamless steel pipe welded by segmented group welding; the welding joint factor is 0.85 when 20% of the circumferential seams are inspected. The fact that a certain authoritative textbook assigns a value of 1 to the welding joint coefficient refers to the (longitudinal) welding joint coefficient used in strength calculations.
One question: For a 3m long seamless steel pipe of DN300, two end caps (elliptical heads) are welded to both ends; 20% of the circumferential joints between the steel pipe and the end caps are to be inspected. What is the welding joint coefficient on the drawing?
For your direct request, just a 100% inspection will do! There are already 2 welds, with a 20% inspection rate; and yet people are still debating whether 0.85 or 1 is the correct value It was a poor design decision from the start
Article 1: Generally, the welding joint coefficient we refer to is applicable to Joint A. Article 2: For the welding coefficient of the head, if it is a welded joint head, the welding coefficient for the cylinder is 0.85; although 100% inspection is carried out (with a qualified inspection level of III), the welding coefficient for the head remains the same as that of the cylinder, namely 0.85. This is my opinion – please correct me if I am wrong.
Personally, I understand it according to wind860811’s view: seamless steel pipes welded in segments are used as the shell, and when 20% of the circumferential seams are inspected, the welding joint factor is 1.
1. Both need to be taken into consideration. 2. They can be considered separately. For seamless steel tube shells welded in sections, the joint coefficient is 1.0; 20% inspection is required for the circumferential seams, and the joint coefficient is specified as longitudinal/circumferential: 1.0/0.85 (without gaskets) or 0.8 (with gaskets). For the heads, 100% RTIII inspection is required, and the joint coefficient for the heads is 0.85
The last edit to this post was made by fzujunru on 2017-11-8 at 16:25; it specifies that the welding joint coefficient should be determined based on Class AB welds.
For the segmented welding of seamless steel tube shells, 20% of the circumferential seams are inspected. The joint coefficient is given as longitudinal/circumferential: 1.0/0.85 (without gaskets) and 0.8 (with gaskets). Should the welding joint coefficient in the calculation sheet be 1 or 0.85?
Calculations generally use the coefficient for longitudinal joints, but the coefficient for circumferential joints is used in shell-and-tube heat exchangers